<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>呼吸灯</title>
  <style>
    

    body{
      border-radius: 50%;
      background-color: red;
      position: absolute;
      left:30%;
      animation: change alternate infinite linear  3s 4s;
    }
    @keyframes change {
      0%{width: 250px;height: 250px;background-color: red;}
      25%{width: 250px;height: 250px;background-color: yellow;}
      50%{width: 250px;height: 250px;background-color: aqua;}
      75%{width: 250px;height: 250px;background-color: blue;}
      100%{width: 250px;height: 250px;background-color: purple;}
    }
    
  </style>
</head>
<body>
  <div></div>
 
</body>
</html>